Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method of transmitting positive-acknowledgement (ACK)/negative-acknowledgement (NACK) for hybrid automatic repeat request (HARQ) in a wireless communication system, and a wireless device using the method.
Related Art
Long term evolution (LTE) based on 3rd generation partnership project (3GPP) technical specification (TS) release 8 is a promising next-generation mobile communication standard. Recently, LTE-advanced (LTE-A) based on 3GPP TS release 10 supporting multiple carriers is under standardization.
As disclosed in 3GPP TS 36.211 V10.2.0 (2011-06) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)”, a physical channel of 3GPP LTE/LTE-A can be classified into a downlink channel, i.e., a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH), and an uplink channel, i.e., a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH).
Recently, an enhanced PDCCH (EPDCCH) for more flexible scheduling of a control channel has been introduced. The EPDCCH supports various schemes such as a search space in a PDSCH region, multiple antenna transmission, etc.
For an HARQ operation, a PDCCH-PUCCH resource linkage is established in 3GPP LTE/LTE-A. Upon receiving the PDCCH, a user equipment sends HARQ ACK/NACK through a PUCCH corresponding to the PDCCH by using a resource linkage. This is to implicitly exchange information about to which transport block the HARQ ACK/NACK belongs between a base station and the user equipment.
The EPDCCH supports a coordinated multi-point (CoMP). In the CoMP operation, the UE receives the EPDCCH from a first base station, and may transmit a corresponding PUCCH to a second base station. That is, this is a case where a downlink base station and an uplink base station are different from each other. Since the base stations are different, there is a need to modify the PDCCH-PUCCH resource linkage.